JOVIAN SYSTEM DATA ANALYSIS PROGRAM PROPOSAL SUMMARY

A crucial issue in understanding resurfacing processes and heat-loss mechanisms on icy satellites is the process of cryomagmatism, which consists of plutonism (intrusion) and volcanism (extrusion). Voyager imaging showed that Ganymede's grooved terrain and Europa's smooth surface were prime candidates for cryovolcanic resurfacing. Galileo images indicate that cryomagmatism is an important process which has operated on these two moons. We propose to evaluate the role of cryomagmatism and the mechanisms of cryovolcanic activity on these bodies based on new Galileo high resolution images and an improved understanding of crustal structure and composition. Specifically, we will 1) define the nature of candidate cryomagmatic activity and deposits and their associations from analysis of Galileo data, 2) provide a synthesis of the range of crustal materials and melts that are candidates for melting and transport to the surface by cryomagmatism (with our collaborator Jeff Kargel), 3) model the ascent, intrusion, and eruption of cryomagmas (including the effects of impurities), 4) use these results to interpret the relative significance of different aspects of cryovolcanism in crustal formation processes on Europa and Ganymede, and 5) use the lessons learned to provide a baseline for other investigators for the interpretation of cryomagmatic processes on other outer planet satellites. The technical approaches and methodologies to be employed in conducting this research include standard image processing and photogeological techniques, using digital image/multispectral data and stereo products, preparation of a range of physical chemistry models and relationships for planetary crusts (provided by J. Kargel), and numerical modeling of the ascent, intrusion, and eruption of cryomagmas (with Lionel Wilson). The proposed research will: 1) provide a basis for the interpretation of cryomagmatic processes in the observed geological record of Ganymede and Europa, 2) link for the first time in a fully integrated way new data on the compostion of the substrate (from observations and theory) with principles of magma generation, migration and emplacment, 3) permit a better understanding of the physics of the ascent and eruption of materials, 4) allow an assessment of the significance of cryomagmatism in the thermal evolution of these bodies, 5) help to formulate a baseline for the interpretation of the geological records of other icy satellites from upcoming Galileo Europa Mission and Cassini Mission data, and 6) help in planning of future missions (e.g., Europa Ocean Explorer). The research proposed is relevant to the specific objectives in the NRA in that it will enhance the scientific return from the Galileo Mission by 'broadening the scientific participation in the analysis and interpretation of the data' (inclusion of Jeff Kargel and Lionel Wilson) and will 'increase the knowledge of the physical state and structure and the dynamic processes acting on the satellites.' It is relevant to future NASA OSS programs and interests from several points of view: scientific, programmatic, and educational/outreach. It provides increased scientific understanding of the Solar System and objects within it and involves new interpretation of data from NASA space flight missions. This research links to the goals of the Origins Program in that the results will provide a better understanding of the environments and mobility of water on Europa and Ganymede and the possible presence of seas or oceans during their geological evolution. Finally, the results of the proposed research have important relevance to present and future NASA Programs (e.g., Cassini Mission, Europa Ocean Explorer, etc.). Although we have not submitted a separate E/PO proposal, we are thoroughly committed to E/PO goals and objectives and plan to develop with Brown University support two modules on 'Water Volcanoes!', and continue with the many public outreach activities in which we are involved. The proposed research is separate from, but related to the activities of the PI as a member of the Galileo SSI Team during the nominal mission, which included the documentation and initial verification of the data, preparation of data release, and providing summaries of the data to the community at large (see references below). The work proposed here involves new collaborators and is separate from the efforts funded during the Galileo Nominal Mission. Head, J.W., and Members of the Galileo Imaging Team, Ganymede: Overview of Solid State Imaging (SSI) findings from the nominal Galileo Mission, Lunar and Planetary Science Conference 29, 1774, 1998. Greeley, R., and Members of the Galileo Imaging Team, Europa in the prime Galileo Mission, Lunar and Planetary Science Conference 29, 1402, 1998.